Inc, June 2006

If you haven't yet heard of VoIP--voice over Internet protocol--you're probably still using a rotary phone. The phenomenon of running phone calls over an Internet connection, through upstart telecom providers such as Vonage, Skype, and Packet8, is growing like mad. There were more than 4.5 million VoIP users in the U.S. last year, and that number will double this year, according to International Data Corp. But while VoIP is a lot less expensive than old-fashioned phone calls, the service hasn't always been so good, and there's been a paucity of features designed specifically for small businesses. Fortunately, VoIP is growing up. Many long-standing concerns--having to do with reliability, sound quality, convenience--have finally been addressed. And scores of new products now make Internet phone systems more powerful than landlines. Here are the six we like best.